There is growing evidence that apnea plays a role in the progression of congestive heart failure (CHF) and that various forms of treatment can lead to improved outcomes. Obstructive sleep apnea (OSA) and central sleep apnea (CSA) occur quite commonly patients with CHF. In general, cardiac output decreases during apnea. For example, in OSA, repetitive pharyngeal collapses have been demonstrated to lower cardiac output by increasing the left ventricular transmural pressure, which is typically defined as the left ventricular pressure minus the intrathoracic pressure (see, e.g., Tkacova et al., “Overnight Shift From Obstructive to Central Apneas in Patients With Heart Failure: Role of PCO2 and Circulatory Delay”, Circulation 2001; 103:238-243).
During airway collapse, intrathoracic pressure decreases substantially and thereby alters ventricular filling, which, in turn, worsens cardiac output. In some instances, such a mechanism may result in a shift from OSA episodes to CSA episodes (see, e.g., Garrigue et al. “Sleep Apnea: A New Indication for Cardiac Pacing?” PACE 27(2):204-211).
Adequate treatment of apnea and the detrimental effects of apnea rely on adequate detection. In particular, a detection technique should be able to distinguish OSA from CSA.
As described herein, various techniques rely on transmural pressure or information related to transmural pressure to detect apneic conditions. Various techniques further include calling for treatment of the conditions or the effects thereof.